CVE-2026-31883: FreeRDP has a `size_t` underflow in ADPCM decoder leads to heap-buffer-overflow write

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.24.0, a sizet underflow in the IMA-ADPCM and MS-ADPCM audio decoders leads to heap-buffer-overflow write via the RDPSND audio channel. In libfreerdp/codec/dsp.c, the IMA-ADPCM and MS-ADPCM decoders subtract block header sizes from a sizet variable without checking for underflow. When nBlockAlign (received from the server) is set such that size % blocksize == 0 triggers the header parsing at a point where size is smaller than the header (4 or 8 bytes), the subtraction wraps size to ~SIZEMAX. The while (size > 0) loop then continues for an astronomical number of iterations. This vulnerability is fixed in 3.24.0.